This invention relates to an outboard motor and more particularly to an improved engine seal and crankcase ventilation arrangement for an outboard motor.
As is well known, internal combustion engines are typically employed as the prime mover for outboard motors. The internal combustion engine positioning in an outboard motor is different from that normally employed in engine applications. Generally, internal combustion engines are mounted so that the crankcase shaft rotates about a horizontally disposed axis.
With an outboard motor, however, the engine is generally mounted so that the crankshaft rotates about a vertically extending axis. This is done so as to facilitate the connection of the crankshaft to the driveshaft which depends into the driveshaft housing and terminates at the lower end thereof where it drives a propulsion device for propelling a watercraft associated with the outboard motor.
The vertical positioning of the crankshaft gives rise to some unique design problems. With two-cycle engines, these problems are somewhat less because lubricant is not normally contained within the crankcase chamber. With a four-cycle engine, on the other hand, lubricant may be contained in the crankcase chamber but this lubricant is stored in a location which is generally removed from the crankcase chamber.
With an outboard motor, however, the outboard motor is frequently tilted up to an out-of-the-water condition even when attached to the watercraft. Furthermore, if the outboard motor is small it may oftentimes be carried in a horizontal position.
In either of the aforenoted conditions, lubricant can flow back into the crankcase chamber. Thus, the upper seal around the uppermost main bearing, considering the situation when the engine is supported vertically, may have to provide assurance that the lubricant cannot flow out of the crankcase chamber in the area around the upper main bearing when the engine crankshaft is horizontal.
Although it is possible to provide seals that prevent such flow, that area may also be utilized for ventilation of the crankcase and blow-by gases from the crankcase chamber. That is, it is desirable to ventilate the crankcase chamber so that the blow-by gases do not build up pressure in it. This can be conveniently done by removing the crankcase gases through the upper wall of the crankcase chamber. However, if there is an open passage, then the loss of lubricant through the path when the engine crankshaft is positioned horizontally can occur.
It is, therefore, a principal object of this invention to provide an improved crankcase seal and crankcase ventilating arrangement that is particularly adaptable for use in outboard motors.
It is a further object of this invention to provide a crankcase seal and ventilating arrangement for an internal combustion engine that provides a ventilating area at one end of the crankshaft and which will permit ventilating gases to flow freely out of the crankcase chamber but will preclude lubricant from flowing through the same path when the engine is positioned horizontally.